Miscabling detection protocol

ABSTRACT

Systems, methods, and non-transitory computer-readable storage media for a miscabling detection protocol. One or more switches can periodically send miscabling protocol (MCP) packets on non-fabric ports on all configured EPG VLANs. A first switch located at a network fabric receives a miscabling protocol (MCP) packet indicating an identity of an originating switch and a port number of an originating port of the MCP packet via a receiving port on the first switch, wherein the MCP packet is received from an external network connected to the receiving port, and wherein the originating switch and originating port are also located at the network fabric and connected to the external network. Based on the MCP packet, the first switch then detects a loop between the receiving port, the originating port, and the external network. Next, the first switch blocks the receiving port or the originating port in response to detecting the loop.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/900,359, filed on Nov. 5, 2013, the content of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present technology pertains to network loops, and more specificallypertains to a miscabling protocol for detecting network loops.

BACKGROUND

The soaring demand for network data throughout the globe has steadilyfueled the evolution of networking technologies, as engineers andmanufacturers rush to keep pace with the changing data consumptionlandscape and increasing network scalability requirements. Variousnetwork technologies have been developed precisely to meet this soaringdemand for network data. For example, overlay network solutions, such asvirtual extensible local area networks (VXLANs), as well asvirtualization and cloud computing technologies, have been widelyimplemented in networks with increasing success as popular solutions tosuch growing demands for network data.

However, while this advancement in network technologies has allowednetworks to support such increased demand for network data, it has alsoresulted in larger and more complex networks, involving massive amountsof traffic data constantly being routed through the network. And as theamount of traffic handled by the network grows, it becomes increasinglyimportant to ensure efficient and error-free routing strategies.Precisely, poor routing strategies can create an enormous burden on thenetwork, which only worsens as the amount of traffic grows, and canresult in inefficient and costly traffic routing, as well as routingerrors, such as route flaps and network loops. Not surprisingly, propercabling and switching configurations are also important for handlinglarge amounts of traffic, as they can help increase network efficiencyand prevent errors, such as network loops. Unfortunately, as thecomplexity of the network grows, it becomes increasingly difficult tomanage the various cabling, switch, and router configurations in thenetwork.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the disclosure can be obtained, a moreparticular description of the principles briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only exemplary embodiments of the disclosure and are nottherefore to be considered to be limiting of its scope, the principlesherein are described and explained with additional specificity anddetail through the use of the accompanying drawings in which:

FIG. 1 illustrates an example network device, according to some aspectsof the subject technology;

FIGS. 2A and 2B illustrate example system embodiments;

FIG. 3 illustrates a schematic block diagram of an example architecturefor a network fabric;

FIG. 4 illustrates an example overlay network;

FIG. 5 illustrates an example network loop;

FIG. 6 illustrates an example loop between a fabric and a layer 2network;

FIG. 7 illustrates an example miscabling protocol packet;

FIG. 8A illustrates an example port operation in non-strict mode;

FIG. 8B illustrates an example port operation in strict mode;

FIG. 9 illustrates a first example method embodiment; and

FIG. 10 illustrates a second example method embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Various embodiments of the disclosure are discussed in detail below.While specific implementations are discussed, it should be understoodthat this is done for illustration purposes only. A person skilled inthe relevant art will recognize that other components and configurationsmay be used without parting from the spirit and scope of the disclosure.

Overview

As previously mentioned, improper cabling, switch, and routerconfigurations can have harmful and even devastating effects on anetwork. For example, improper cabling or port configurations in anetwork can result in a layer 2 forwarding loop being formed in thenetwork. A loop in the network can severely undermine and often cripplethe network. In some cases, depending on the external connection, a loopcan even create a fatal meltdown in the network. Moreover, a network canbe particularly susceptible to a fatal meltdown when broadcast ormulticast messages are transmitted through links that are connected intoa loop. Yet as new, larger networks and more complex configurations areimplemented in a network environment, error detection and correction,such as loop detection and correction, become a significant challengefor network engineers.

Unfortunately, however, current solutions fail to provide adequateprevention against improper cabling and port configurations,particularly on larger, more complex environments, and lack effectivemechanisms for intelligently and dynamically detecting such miscablingand improper port configurations. Thus, it would be advantageous toimplement a mechanism that allows for intelligent and efficientdetection and correction of miscabling and improper port configurations,to prevent the damaging consequences of network loops.

The approaches set forth herein can be implemented to address theforegoing issues, for example, by detecting a loop in a network andperforming a corrective action, such as blocking or re-configuring oneor more links in the loop. Specifically, these approaches can be used toimplement a miscabling protocol in the fabric. The miscabling protocolcan ascertain which front panel port(s) (i.e., non-fabric port(s)) isconnected to another front panel port in the same flood domain, suchthat both front panel ports are improperly configured in a loop in thebridge domain.

There are various configurations or scenarios which can result in anetwork loop. For example, if the ports are directly connected to eachother, this can create a loop with a potential meltdown scenario, whereany packet egressing on one of the ports will loop forever. If it is amulticast or broadcast packet, it can exponentially increase the load onthe network, as each time the packet loops, the packet will createmultiple copies of itself which are sent to the rest of the flooddomain.

Another configuration or scenario can result in a loop if the ports areinter-connected by a layer 2 (L2) network which is running spanning treeprotocol (STP). Here, one of the ports would likely be blocked by STP.The fabric would forward bridge protocol data units (BPDUs) throughspine switches, and thus the STP-aware external L2 switches willdiscover the fabric as an L2 link. STP would likely block the ports inthis scenario to break the loop. The topology here would look like atriangle formed between the inter-connected ports and the L2 network.

Finally, the next scenario can result in a problematic configurationcase, or even a meltdown. For example, if two ports in the fabric, sayport 1 (“P1”) and port 2 (“P2”), are connected to an external L2 networkand marked to be part of different endpoint groups (EPGs) or virtualLANs (VLANs), but actually belong to the same bridge domain (BD), yetfrom the L2 network side, these ports are part of the same VLAN, thisconfiguration would result in a loop and STP would not work to breaksuch loop. STP BPDUs would be flooded over a specific EPG-VLAN, but notthe BD. Because STP BPDUs do not cross EPG-VLANs, the L2 networkswitches will not discover any BPDU sent on one port (with that port'sEPG-VLAN) over the other port. As such, the L2 network will keep theports in forward state (MCP_FWD state). Yet from the fabric's point ofview, both of these ports are part of the same flood domain (i.e., sameBD). Thus, the classic L2 loop will be formed, as discussed above.

Disclosed are systems, methods, and non-transitory computer-readablestorage media for implementing a miscabling protocol in overlaynetworks. As follows, a method of the subject technology is describedwith respect to a system performing steps for loop detection. Here, thesystem can refer to a device, such as a network device, including aswitch, as described further below.

The system receives a miscabling protocol (MCP) packet indicating anidentity of an originating switch and a port number of an originatingport of the MCP packet. The system receives the MCP packet via areceiving port on the system.

The system and originating switch can be located on the same networkfabric and connected to the same external network. For example, thesystem and originating switch can be leaf switches in the fabric.Moreover, the system and originating switch can be top-of-rack (ToR)switches. In some embodiments, the external network is an L2 network.

Based on the MCP packet, the system detects identifies a loop betweenthe receiving port, the originating port, and the external network. Thesystem can detect the loop based on a receipt of the MCP packet, as theMCP packet is not intended to return to the fabric after it leaves theoriginating port. The originating port can be a non-fabric portconfigured to periodically send the MCP packets to a multicast address,such as an MCP or STP multicast address. In some cases, the systemand/or the originating switch can be configured to send an MCP packetfor each configured EPG or VLAN.

When receiving the MCP packet, the system can extract the identity ofthe originating switch and the port number to determine that a loop doesindeed exist. Here, the system can use that information to determinethat another switch in the fabric sent the MCP packet, and the MCPpacket looped back from an external network back to the fabric.

Next, the system can block the receiving port and/or the originatingport in response to detecting the loop. In some cases, the system canuse the identity and port number in the MCP packet to determine whichport should be blocked. For example, the system can check if it shouldblock the receiving port, and make a determination based on a priorityof the originating switch and port vis-à-vis the system and receivingport. The system can determine priorities based on the respectiveaddresses of the switches, such as the IP addresses of the system andoriginating switch, as well as the port numbers of the originating andreceiving ports. In some cases, the switch and port with the higher IPaddress can be blocked over the switch and port with the lower IPaddress. For example, if the system receives the MCP packet from anoriginating switch that has a lower IP address, as determined based onthe MCP packet, the system would then block its receiving port.

To break the loop, the system administrator (“sys admin”) can correctthe miscabling or shut the trouble port off through a shut command.Alternatively, the system can block the port to prevent traffic beingforwarded into a loop, and thus break the loop. Here, the port can beset to a block state. However, in some cases, the port can be placed ina state were traffic is blocked with some exemptions. Exemptions can beprovided for certain types of traffic, such as MCP or STP traffic, forexample. In some cases, the blocked port can be restored to a forwardingstate after a timeout period of time, which can be a configurationparameter, or an explicit command from the sys admin.

By detecting and breaking loops between the leaf or ToR switches in thefabric and the external network, the miscabling protocol can helpprevent, detect, and correct loops in overlay networks, such as VXLANs.

DESCRIPTION

A computer network is a geographically distributed collection of nodesinterconnected by communication links and segments for transporting databetween endpoints, such as personal computers and workstations. Manytypes of networks are available, with the types ranging from local areanetworks (LANs) and wide area networks (WANs) to overlay andsoftware-defined networks, such as virtual extensible local areanetworks (VXLANs).

LANs typically connect nodes over dedicated private communications linkslocated in the same general physical location, such as a building orcampus. WANs, on the other hand, typically connect geographicallydispersed nodes over long-distance communications links, such as commoncarrier telephone lines, optical lightpaths, synchronous opticalnetworks (SONET), or synchronous digital hierarchy (SDH) links. LANs andWANs can include layer 2 (L2) and/or layer 3 (L3) networks and devices.

The Internet is an example of a WAN that connects disparate networksthroughout the world, providing global communication between nodes onvarious networks. The nodes typically communicate over the network byexchanging discrete frames or packets of data according to predefinedprotocols, such as the Transmission Control Protocol/Internet Protocol(TCP/IP). In this context, a protocol can refer to a set of rulesdefining how the nodes interact with each other. Computer networks maybe further interconnected by an intermediate network node, such as arouter, to extend the effective “size” of each network.

Overlay networks generally allow virtual networks to be created andlayered over a physical network infrastructure. Overlay networkprotocols, such as Virtual Extensible LAN (VXLAN), NetworkVirtualization using Generic Routing Encapsulation (NVGRE), NetworkVirtualization Overlays (NVO3), and Stateless Transport Tunneling (STT),provide a traffic encapsulation scheme which allows network traffic tobe carried across L2 and L3 networks over a logical tunnel. Such logicaltunnels can be originated and terminated through virtual tunnel endpoints (VTEPs).

Moreover, overlay networks can include virtual segments, such as VXLANsegments in a VXLAN overlay network, which can include virtual L2 and/orL3 overlay networks over which VMs communicate. The virtual segments canbe identified through a virtual network identifier (VNI), such as aVXLAN network identifier, which can specifically identify an associatedvirtual segment or domain.

Network virtualization allows hardware and software resources to becombined in a virtual network. For example, network virtualization canallow multiple numbers of VMs to be attached to the physical network viarespective virtual LANs (VLANs). The VMs can be grouped according totheir respective VLAN, and can communicate with other VMs as well asother devices on the internal or external network.

Network segments, such as physical or virtual segments; networks;devices; ports; physical or logical links; and/or traffic in general canbe grouped into a bridge or flood domain. A bridge domain or flooddomain can represent a broadcast domain, such as an L2 broadcast domain.A bridge domain or flood domain can include a single subnet, but canalso include multiple subnets. Moreover, a bridge domain can beassociated with a bridge domain interface on a network device, such as aswitch. A bridge domain interface can be a logical interface whichsupports traffic between an L2 bridged network and an L3 routed network.In addition, a bridge domain interface can support internet protocol(IP) termination, VPN termination, address resolution handling, MACaddressing, etc. Both bridge domains and bridge domain interfaces can beidentified by a same index or identifier.

Furthermore, endpoint groups (EPGs) can be used in a network for mappingapplications to the network. In particular, EPGs can use a grouping ofapplication endpoints in a network to apply connectivity and policy tothe group of applications. EPGs can act as a container for buckets orcollections of applications, or application components, and tiers forimplementing forwarding and policy logic. EPGs also allow separation ofnetwork policy, security, and forwarding from addressing by insteadusing logical application boundaries.

Cloud computing can also be provided in one or more networks to providecomputing services using shared resources. Cloud computing can generallyinclude Internet-based computing in which computing resources aredynamically provisioned and allocated to client or user computers orother devices on-demand, from a collection of resources available viathe network (e.g., “the cloud”). Cloud computing resources, for example,can include any type of resource, such as computing, storage, andnetwork devices, virtual machines (VMs), etc. For instance, resourcesmay include service devices (firewalls, deep packet inspectors, trafficmonitors, load balancers, etc.), compute/processing devices (servers,CPU's, memory, brute force processing capability), storage devices(e.g., network attached storages, storage area network devices), etc. Inaddition, such resources may be used to support virtual networks,virtual machines (VM), databases, applications (Apps), etc.

Cloud computing resources may include a “private cloud,” a “publiccloud,” and/or a “hybrid cloud.” A “hybrid cloud” can be a cloudinfrastructure composed of two or more clouds that inter-operate orfederate through technology. In essence, a hybrid cloud is aninteraction between private and public clouds where a private cloudjoins a public cloud and utilizes public cloud resources in a secure andscalable manner. Cloud computing resources can also be provisioned viavirtual networks in an overlay network, such as a VXLAN.

The disclosed technology addresses the need in the art for accurate andefficient detection of network loops in a network, such as an overlaynetwork and a network fabric. Disclosed are systems, methods, andcomputer-readable storage media for a miscabling detection protocol. Abrief introductory description of exemplary systems and networks, asillustrated in FIGS. 1 through 4, is disclosed herein. A detaileddescription of miscabling protocol, related concepts, and exemplaryvariations, will then follow. These variations shall be described hereinas the various embodiments are set forth. The disclosure now turns toFIG. 1.

FIG. 1 illustrates an exemplary network device 110 suitable forimplementing the present invention. Network device 110 includes a mastercentral processing unit (CPU) 162, interfaces 168, and a bus 115 (e.g.,a PCI bus). When acting under the control of appropriate software orfirmware, the CPU 162 is responsible for executing packet management,error detection, and/or routing functions, such as miscabling detectionfunctions, for example. The CPU 162 preferably accomplishes all thesefunctions under the control of software including an operating systemand any appropriate applications software. CPU 162 may include one ormore processors 163 such as a processor from the Motorola family ofmicroprocessors or the MIPS family of microprocessors. In an alternativeembodiment, processor 163 is specially designed hardware for controllingthe operations of router 110. In a specific embodiment, a memory 161(such as non-volatile RAM and/or ROM) also forms part of CPU 162.However, there are many different ways in which memory could be coupledto the system.

The interfaces 168 are typically provided as interface cards (sometimesreferred to as “line cards”). Generally, they control the sending andreceiving of data packets over the network and sometimes support otherperipherals used with the router 110. Among the interfaces that may beprovided are Ethernet interfaces, frame relay interfaces, cableinterfaces, DSL interfaces, token ring interfaces, and the like. Inaddition, various very high-speed interfaces may be provided such asfast token ring interfaces, wireless interfaces, Ethernet interfaces,Gigabit Ethernet interfaces, ATM interfaces, HSSI interfaces, POSinterfaces, FDDI interfaces and the like. Generally, these interfacesmay include ports appropriate for communication with the appropriatemedia. In some cases, they may also include an independent processorand, in some instances, volatile RAM. The independent processors maycontrol such communications intensive tasks as packet switching, mediacontrol and management. By providing separate processors for thecommunications intensive tasks, these interfaces allow the mastermicroprocessor 162 to efficiently perform routing computations, networkdiagnostics, security functions, etc.

Although the system shown in FIG. 1 is one specific network device ofthe present invention, it is by no means the only network devicearchitecture on which the present invention can be implemented. Forexample, an architecture having a single processor that handlescommunications as well as routing computations, etc. is often used.Further, other types of interfaces and media could also be used with therouter.

Regardless of the network device's configuration, it may employ one ormore memories or memory modules (including memory 161) configured tostore program instructions for the general-purpose network operationsand mechanisms for roaming, route optimization and routing functionsdescribed herein. The program instructions may control the operation ofan operating system and/or one or more applications, for example. Thememory or memories may also be configured to store tables such asmobility binding, registration, and association tables, etc.

FIG. 2A, and FIG. 2B illustrate exemplary possible system embodiments.The more appropriate embodiment will be apparent to those of ordinaryskill in the art when practicing the present technology. Persons ofordinary skill in the art will also readily appreciate that other systemembodiments are possible.

FIG. 2A illustrates a conventional system bus computing systemarchitecture 200 wherein the components of the system are in electricalcommunication with each other using a bus 205. Exemplary system 200includes a processing unit (CPU or processor) 210 and a system bus 205that couples various system components including the system memory 215,such as read only memory (ROM) 220 and random access memory (RAM) 225,to the processor 210. The system 200 can include a cache of high-speedmemory connected directly with, in close proximity to, or integrated aspart of the processor 210. The system 200 can copy data from the memory215 and/or the storage device 230 to the cache 212 for quick access bythe processor 210. In this way, the cache can provide a performanceboost that avoids processor 210 delays while waiting for data. These andother modules can control or be configured to control the processor 210to perform various actions. Other system memory 215 may be available foruse as well. The memory 215 can include multiple different types ofmemory with different performance characteristics. The processor 210 caninclude any general purpose processor and a hardware module or softwaremodule, such as module 1 232, module 2 234, and module 3 236 stored instorage device 230, configured to control the processor 210 as well as aspecial-purpose processor where software instructions are incorporatedinto the actual processor design. The processor 210 may essentially be acompletely self-contained computing system, containing multiple cores orprocessors, a bus, memory controller, cache, etc. A multi-core processormay be symmetric or asymmetric.

To enable user interaction with the computing device 200, an inputdevice 245 can represent any number of input mechanisms, such as amicrophone for speech, a touch-sensitive screen for gesture or graphicalinput, keyboard, mouse, motion input, speech and so forth. An outputdevice 235 can also be one or more of a number of output mechanismsknown to those of skill in the art. In some instances, multimodalsystems can enable a user to provide multiple types of input tocommunicate with the computing device 200. The communications interface240 can generally govern and manage the user input and system output.There is no restriction on operating on any particular hardwarearrangement and therefore the basic features here may easily besubstituted for improved hardware or firmware arrangements as they aredeveloped.

Storage device 230 is a non-volatile memory and can be a hard disk orother types of computer readable media which can store data that areaccessible by a computer, such as magnetic cassettes, flash memorycards, solid state memory devices, digital versatile disks, cartridges,random access memories (RAMs) 225, read only memory (ROM) 220, andhybrids thereof.

The storage device 230 can include software modules 232, 234, 236 forcontrolling the processor 210. Other hardware or software modules arecontemplated. The storage device 230 can be connected to the system bus205. In one aspect, a hardware module that performs a particularfunction can include the software component stored in acomputer-readable medium in connection with the necessary hardwarecomponents, such as the processor 210, bus 205, display 235, and soforth, to carry out the function.

FIG. 2B illustrates a computer system 250 having a chipset architecturethat can be used in executing the described method and generating anddisplaying a graphical user interface (GUI). Computer system 250 is anexample of computer hardware, software, and firmware that can be used toimplement the disclosed technology. System 250 can include a processor255, representative of any number of physically and/or logicallydistinct resources capable of executing software, firmware, and hardwareconfigured to perform identified computations. Processor 255 cancommunicate with a chipset 260 that can control input to and output fromprocessor 255. In this example, chipset 260 outputs information tooutput 265, such as a display, and can read and write information tostorage device 270, which can include magnetic media, and solid statemedia, for example. Chipset 260 can also read data from and write datato RAM 275. A bridge 280 for interfacing with a variety of userinterface components 285 can be provided for interfacing with chipset260. Such user interface components 285 can include a keyboard, amicrophone, touch detection and processing circuitry, a pointing device,such as a mouse, and so on. In general, inputs to system 250 can comefrom any of a variety of sources, machine generated and/or humangenerated.

Chipset 260 can also interface with one or more communication interfaces290 that can have different physical interfaces. Such communicationinterfaces can include interfaces for wired and wireless local areanetworks, for broadband wireless networks, as well as personal areanetworks. Some applications of the methods for generating, displaying,and using the GUI disclosed herein can include receiving ordereddatasets over the physical interface or be generated by the machineitself by processor 255 analyzing data stored in storage 270 or 275.Further, the machine can receive inputs from a user via user interfacecomponents 285 and execute appropriate functions, such as browsingfunctions by interpreting these inputs using processor 255.

It can be appreciated that exemplary systems 200 and 250 can have morethan one processor 210 or be part of a group or cluster of computingdevices networked together to provide greater processing capability.

FIG. 3 illustrates a schematic block diagram of an example architecture300 for a network fabric 312. The network fabric 312 can include spineswitches 302A, 302B, . . . , 302C (collectively “302”) connected to leafswitches 304A, 304B, 304C, . . . , 304D (collectively “304”) in thenetwork fabric 312.

Spine switches 302 can be Layer 3 (“L3”) switches in the fabric 312.However, in some cases, the spine switches 302 can also, or otherwise,perform Layer 2 (“L2”) functionalities. Further, the spine switches 302can support various capabilities, such as 40 or 10 Gbps Ethernet speeds.To this end, the spine switches 302 can include one or more 40 GigabitEthernet ports. Each port can also be split to support other speeds. Forexample, a 40 Gigabit Ethernet port can be split into four 10 GigabitEthernet ports.

In some embodiments, one or more of the spine switches 302 can beconfigured to host a proxy function that performs a lookup of theendpoint address identifier to locator mapping in a mapping database onbehalf of leaf switches 304 that do not have such mapping. The proxyfunction can do this by parsing through the packet to the encapsulated,tenant packet to get to the destination locator address of the tenant.The spine switches 302 can then perform a lookup of their local mappingdatabase to determine the correct locator address of the packet andforward the packet to the locator address without changing certainfields in the header of the packet.

When a packet is received at a spine switch 302 _(i), the spine switch302 _(i) can first check if the destination locator address is a proxyaddress. If so, the spine switch 302 _(i) can perform the proxy functionas previously mentioned. If not, the spine switch 302 _(i) can lookupthe locator in its forwarding table and forward the packet accordingly.

Spine switches 302 connect to leaf switches 304 in the fabric 312. Leafswitches 304 can include access ports (or non-fabric ports) and fabricports. Fabric ports can provide uplinks to the spine switches 302, whileaccess ports can provide connectivity for devices, hosts, endpoints,VMs, or external networks to the fabric 312.

Leaf switches 304 can reside at the edge of the fabric 312, and can thusrepresent the physical network edge. In some cases, the leaf switches304 can be top-of-rack (“ToR”) switches configured according to a ToRarchitecture. In other cases, the leaf switches 304 can be aggregationswitches in any particular topology, such as end-of-row (EoR) ormiddle-of-row (MoR) topologies.

The leaf switches 304 can be responsible for routing and/or bridging thetenant packets and applying network policies. In some cases, a leafswitch can perform one or more additional functions, such asimplementing a mapping cache, sending packets to the proxy function whenthere is a miss in the cache, encapsulate packets, enforce ingress oregress policies, etc.

Moreover, the leaf switches 304 can contain virtual switchingfunctionalities, such as a virtual tunnel endpoint (VTEP) function asexplained below in the discussion of VTEP 408 in FIG. 4. To this end,leaf switches 304 can connect the fabric 312 to an overlay network, suchas overlay network 400 illustrated in FIG. 4.

Network connectivity in the fabric 312 can flow through the leafswitches 304. Here, the leaf switches 304 can provide servers,resources, endpoints, external networks, or VMs access to the fabric312, and can connect the leaf switches 304 to each other. In some cases,the leaf switches 304 can connect endpoint groups (“EPGs”) to the fabric312 and/or any external networks. Each EPG can connect to the fabric 312via one of the leaf switches 304, for example.

Endpoints 310A-E (collectively “310”) can connect to the fabric 312 vialeaf switches 304. For example, endpoints 310A and 310B can connectdirectly to leaf switch 304A, which can connect endpoints 310A and 310Bto the fabric 312 and/or any other of the leaf switches 304. Similarly,endpoint 310E can connect directly to leaf switch 304C, which canconnect endpoint 310E to the fabric 312 and/or any other of the leafswitches 304. On the other hand, endpoints 310C and 310D can connect toleaf switch 304B via L2 network 306. Similarly, the wide area network(WAN) can connect to the leaf switches 304C or 304D via L3 network 308.

Endpoints 310 can include any communication device, such as a computer,a server, a switch, etc. In some cases, the endpoints 310 can include aserver or switch configured with a virtual tunnel endpoint functionalitywhich connects an overlay network, such as overlay network 400 below,with the fabric 312. For example, in some cases, the endpoints 310 canrepresent the virtual tunnel endpoints 408A-D illustrated in FIG. 4. Theoverlay network can host physical devices, such as servers,applications, EPGs, virtual segments, virtual workloads, etc. Likewise,endpoints 310 can also host virtual workloads and applications, whichcan connect with the fabric 312 or any other device or network,including an external network.

FIG. 4 illustrates an exemplary overlay network 400. Overlay network 400uses an overlay protocol, such as VXLAN, VGRE, VO3, or STT, toencapsulate traffic in L2 and/or L3 packets which can cross overlay L3boundaries in the network. As illustrated in FIG. 4, overlay network 400can include hosts 406A-D interconnected via network 402.

Network 402 can include any packet network, such as an IP network, forexample. Moreover, hosts 406A-D include virtual tunnel end points (VTEP)408A-D, which can be virtual nodes or switches configured to encapsulateand de-encapsulate data traffic according to a specific overlay protocolof the network 400, for the various virtual network identifiers (VNIDs)410A-I. In some embodiments, network 400 can be a VXLAN network, andVTEPs 408A-D can be VXLAN tunnel end points.

The VNIDs can represent the segregated virtual networks in overlaynetwork 400. Each of the overlay tunnels (VTEPs 408A-D) can include oneor more VNIDs. For example, VTEP 408A can include VNIDs 1 and 2, VTEP408B can include VNIDs 1 and 3, VTEP 408C can include VNIDs 1 and 2, andVTEP 408D can include VNIDs 1-3. As one of ordinary skill in the artwill readily recognize, any particular VTEP can, in other embodiments,have numerous VNIDs, including more than the 3 VNIDs illustrated in FIG.4.

The traffic in overlay network 400 can be segregated logically accordingto specific VNIDs. This way, traffic intended for VNID 1 can be accessedby devices residing in VNID 1, while other devices residing in otherVNIDs (e.g., VNIDs 2 and 3) can be prevented from accessing suchtraffic. In other words, devices or endpoints connected to specificVNIDs can communicate with other devices or endpoints connected to thesame specific VNIDs, while traffic from separate VNIDs can be isolatedto prevent devices or endpoints in other specific VNIDs from accessingtraffic in different VNIDs.

Endpoints and VMs 404A-I can connect to their respective VNID or virtualsegment, and communicate with other endpoints or VMs residing in thesame VNID or virtual segment. For example, endpoint 404A can communicatewith endpoint 404C and VMs 404E, G because they all reside in the sameVNID, namely, VNID 1. Similarly, endpoint 404B can communicate with VMs404F, H because they all reside in VNID 2.

VTEPs 408A-D can encapsulate packets directed at the various VNIDs 1-3in the overlay network 400 according to the specific overlay protocolimplemented, such as VXLAN, so traffic can be properly transmitted tothe correct VNID and recipient(s). Moreover, when a switch, router, orother network device receives a packet to be transmitted to a recipientin the overlay network 400, it can analyze a routing table, such as alookup table, to determine where such packet needs to be transmitted sothe traffic reaches the appropriate recipient. For example, if VTEP 408Areceives a packet from endpoint 404B that is intended for endpoint 404H,VTEP 408A can analyze a routing table that maps the intended endpoint,endpoint 404H, to a specific switch that is configured to handlecommunications intended for endpoint 404H. VTEP 408A might not initiallyknow, when it receives the packet from endpoint 404B, that such packetshould be transmitted to VTEP 408D in order to reach endpoint 404H.Accordingly, by analyzing the routing table, VTEP 408A can lookupendpoint 404H, which is the intended recipient, and determine that thepacket should be transmitted to VTEP 408D, as specified in the routingtable based on endpoint-to-switch mappings or bindings, so the packetcan be transmitted to, and received by, endpoint 404H as expected.

However, continuing with the previous example, in many instances, VTEP408A may analyze the routing table and fail to find any bindings ormappings associated with the intended recipient, e.g., endpoint 404H.Here, the routing table may not yet have learned routing informationregarding endpoint 404H. In this scenario, the VTEP 408A may likelybroadcast or multicast the packet to ensure the proper switch associatedwith endpoint 404H can receive the packet and further route it toendpoint 404H.

In some cases, the routing table can be dynamically and continuouslymodified by removing unnecessary or stale entries and adding new ornecessary entries, in order to maintain the routing table up-to-date,accurate, and efficient, while reducing or limiting the size of thetable.

As one of ordinary skill in the art will readily recognize, the examplesand technologies provided above are simply for clarity and explanationpurposes, and can include many additional concepts and variations.

FIG. 5 illustrates an example configuration 500 of a network loop 508.The network loop 508 can flow through ports 502-506. The network loop508 can be a traditional L2 loop or forwarding loop. The loop 508 can bethe result of a miscabling error and/or a bad configuration on the ports502-506. Thus, the loop 508 will continue until the cabling iscorrected, one of the ports 502-506 is blocked, or otherwise when thenetwork is crippled or reconfigured.

In particular, the loop 508 is created when a packet is transmitted onone of the ports 502-506 and forwarded throughout the ports 502-506 in aloop. For example, if the ports 502-506 are interconnected and all areset to forwarding mode, the packet will continue to be forwardedthroughout the ports 502-506 in a loop.

If a broadcast or multicast packet is transmitted by one of the ports502, the traffic generated by the loop 508 can cripple the network andresult in a meltdown scenario. Here, the broadcast or multicast packetwill exponentially increase the load on the network by creating multiplecopies of itself each time the packet loops. Eventually, the load mayoverburden the network causing a fatal meltdown of the network.

The ports 502-506 can reside on one or more switches. The switches caninclude physical switches, such as ToRs, and/or virtual switches, suchas software switches or a hypervisor running a VTEP function. Moreover,the switches can reside on one or more networks, including L2 networks,VLANs, EPGs, overlay networks, L3 networks, etc.

If the ports 502-506 reside on the same device, the loop 508 can be aself-loop resulting from a packet looping among the ports 502-506 on thesame device. Here, the loop 508 can be corrected by blocking one of theports 502-506, reconfiguring the device, and/or reconfiguring one ormore ports 502-506.

FIG. 6 illustrates an example loop 600 between a fabric 312 and an L2network 306. The fabric 312 can include one or more ToR switches hostingToR ports 1 and 2 (602, 604). ToR ports 1 and 2 (602, 604) can connectthe fabric 312 to L2 network 306. Moreover, the ToR ports 1 and 2 (602,604) can be interconnected through L2 network 306. This interconnectionbetween ToR ports 1 and 2 (602, 604), through L2 network 306, can resultin a loop 600. In particular, loop 600 can form when the connections tothe L2 network 306 on ToR ports 1 and 2 (602, 604) are set to belong tothe same bridge domain (“BD”) but different VLANs or EPGs, while the ToRports 1 and 2 (602, 604) are marked on the L2 network 306 as part of thesame VLAN.

For example, if the L2 network 306 is configured on ToR port 1 (602) asbeing on VLAN 50 and BD 1, while the L2 network 306 is configured on ToRport 2 (604) as being on the same BD 1 but VLAN 60 (as opposed to VLAN50), and ToR ports 1 and 2 (602, 604) are both marked on the L2 network306 as being on VLAN 10, this can result in the loop 600. Here, ToRports 1 and 2 would be interconnected by the L2 network 306 in atriangle such that packets will traverse the connection in a loop.

In such a case STP would not break the loop 600. STP BPDUs are floodedover a VLAN, but not through the BD. Because STP BPDUs do not crossdifferent VLANs, the switches in the L2 network 306 will not discoverany BPDUs sent on one port (with that ports vlan) over other ports. Assuch, the L2 network 306 will keep the ports in forwarding state (i.e.,MCP_FWD state). However, from the point of view of the fabric 312, bothports are part of the same flood-domain (same BD). Thus, the loop 600will be formed and packets egressed through one of the ToR ports 1 and 2will be returned to the fabric through the L2 network 306.

To detect loop 600 in this scenario, the leaf switches on the fabric 312can be configured to support a miscabling protocol that is instantiatedon the non-fabric ports of leaf switches 304. Any miscabling ormisconfiguration between spine switches 302 and leaf switches 304 can behandled by IFC discovery protocol. The miscabling protocol can beconfigured on the access layer switches, such as ToR/leaf switches, andimplemented along with STP, which can be configured to run on externalL2 switches.

With the miscabling protocol, the ToR switches (e.g., leaf switches 304)can be configured to periodically send out a miscabling protocol packet(“MCP”) on non-fabric ports. The MCP can be sent for each configuredEPG-VLAN. The ToR switches can be then configured to detect a loopanytime an MCP ingresses on one of their ports by analyzing the contentof the MCP.

The miscabling protocol packet data unit (PDU) can be an L2 packet sentto a multicast address, such as a CDP or STP multicast address. The MCPcan be an LLC-SNAP encapsulation with a new SAP type. Each ToR switchcan be responsible for sending out MCPs with a configurable periodicityor according to a specific interval or schedule.

When a port is inited, it goes in MCP forwarding state (MCP_FWD state).The payload of the MCP can contain the identity of the originating ToRswitch, such as the address of the ToR switch; the port number of theoriginating ToR switch; a timestamp; and/or a checksum, such as MD-5 orSHA-1 checksum, which can be based on a pre-shared key. In some cases,to support the control plane overhead, the ToR switches can use hardwareassist when generating MCP packets.

A ToR switch should not see any MCP packets ingressed from its ports, asthis indicates a loop. In some cases, when receiving an MCP, thereceiving ToR switch can first use the configured pre-shared key toderive the checksum and verify whether it matches the checksum receivedin the packet to determine if the packet is an attack packet or anauthentic packet. If the MCP is not a valid packet, as determined by thechecksum, the ToR can silently drop it. In some cases, the ToR switchcan also generate a syslog message. The message can alert IFC of apossible (malicious) attack.

Next, the ToR switch can check if the time stamp is within a thresholdamount of time. If the time stamp is not in an acceptable window of time(e.g., current time stamp at the received ToR with a difference of xseconds above a configured threshold), then the packet can also bedropped and IFC alerted of a possible replay attack.

If both the checksum and time stamp checks pass, the ToR switch candetermine whether it should block the receiving port or the sendingport. In some embodiments, the switch determines which port to block bycomparing priorities and/or identities associated with the receiving andsending switches. For example, the receiving ToR switch can check if theoriginating switch has lower IP address than the receiving ToR switch.If so, the receiving ToR switch can block the port on which the packetingressed. Alternatively, the sending ToR switch can block the sendingport where the packet egressed. This can be achieved by having thereceiving switch send a message to the originating switch about themiscabling or loop detected. This can otherwise be achieved when theroles of the switches change. For example, when the current receiverswitch originates its own MCP packet and the previous sending switchreceives this MCP packet, at that point the previous sending switch canblock the ingress port.

If the originating switch identity matches the receiving switch'sidentity (self-loop), then the switch can check if the port number ofthe packet is less than or equal to the port number on which the packetwas received. If so, the ingress port can be blocked (error-disabled)and is not allowed to send or receive any user traffic. However, in somecases, the ingress port can be set to allow certain types of traffic,such as MCP or STP packets, for example. An admin shut/no-shut willclear the port state to forwarding, MCP_FWD state.

The miscabling protocol can also help prevent, detect, and correct loopsin an overlay network, such as a VXLAN network. For example, if ToRports 1 and/or 2 are connected to an overlay network, such as overlaynetwork 400, the miscabling protocol can prevent ToR ports 1 and/or 2from forwarding traffic to VLANs in the overlay network that belong tothe BD. Blocking one of the ToR ports in the loop can ensure thattraffic in the overlay network is not continuously forwarded in a loop.This can particularly help an overlay network which cannot use STP tobreak any loops.

Referring now to FIG. 7, an example miscabling protocol packet (MCP) 700can include a switch identity 702 and port number 704. The switchidentity can refer to the identity of the originating switch, which hasgenerated and transmitted the MCP. The identity can include an IPaddress, such as a loopback IP address. However, in some embodiments,the identity 702 can be the switch's MAC address, hardware address, orany other address and/or identifying string.

Similarly, the port number 704 can refer to the originating port numberon the originating switch. The MCP 700 can also include a timestamp 706,which can indicate when the MCP was generated and/or transmitted. Thisway, a receiving switch can compare the timestamp 706 with the time ofreceipt to determine if the packet was sent as part of an attack, suchas a replay attack.

The MCP 700 can also include a checksum 708. The checksum can be createdbased on a pre-shared key, which allows the receiving device to use thepre-shared key to verify the checksum. The checksum 708 can be based ona checksum function or algorithm. In some cases, the checksum 708 can bean MD5 checksum. In other embodiments, the checksum 708 can be a SHAchecksum, such as a SHA1 checksum. However, as one of ordinary skill inthe art will readily recognize, the checksum 708 can be based on anyother checksum function or algorithm, including those currentlyavailable and any available in the future.

In some embodiments, the MCP 700 can also include more or less fields orportions of information. For example, in some cases, the MCP 700 caninclude a second identity, such as a second address; networkinformation; protocol information; a flag, such as a VLAN flag; etc. Theexamples provided above are for illustration purposes. Other embodimentsare contemplated herein.

FIG. 8A illustrates an example port operation 800 in non-strict mode. Aport can first receive a port up command 802 to place the port onforwarding mode 804. The port can be a non-fabric port on a fabricnetwork, such as fabric 312. For example, the port can be a non-fabricport on a leaf switch 304, on the fabric 312.

While in forwarding mode 804, the port can forward packets it receivesthat are not destined for port. For example, MCP packets can be sent toa multicast address, such as an MCP or STP multicast address. Thus, ifport receives a packet addressed to the multicast address, it canautomatically forward the packet based on a determination that the portis not the intended recipient.

When up, the port can also send periodic MCP packets 806 as part of themiscabling protocol for detecting loops. Here, the periods for sendingthe MCP packets can be based on a configuration parameter, a schedule,an event, etc. The periodic MCP packets can allow the ToR switches tocontinuously check for loops. Since the MCP packets are transmitted to amulticast address, ToR switches should not receive any MCP packets onits ports unless a loop exists. Thus, if a port on a ToR switch receivesan MCP packet, the ToR switch can assume or ascertain that the MCPpacket was received as a result of a forwarding loop. This can mean thatan originating ToR switch transmitted the MCP packet from one of itsnon-fabric ports, and the MCP packet was forwarded until it was laterreturned to a ToR switch in the fabric 312, including the originatingToR switch and/or any other ToR switch.

As previously suggested, if the port receives an MCP packet 808, it canbe set to a blocked state 810 to prevent the port from forwardingtraffic in a loop in the network. In some embodiments, the receivingport is set to a blocked state 810 when it receives an MCP packet 808from an originating switch and port having a lower identity than that ofthe receiving switch and port. In other embodiments, the originatingswitch can block the originating port when the receiving switch and porthave a lower identity than that of the originating port and switch.

To perform the comparison of identities, the receiving switch canextract the identity of the originating switch from the MCP packet 808,and compare the identity of the originating switch with the identity ofthe receiving switch to determine whether it should be set to block. Theidentity of a switch can be based on the address of the switch, such asthe IP or MAC address of the switch; the port number of the switch; thenetwork associated with the switch, such as the VLAN of the switch orthe subnet of the switch; the hardware address of the switch; etc. Insome embodiments, the identity is determined based on the IP address ofthe switch. In other embodiments, the identity is determined based on acombination of the address, such as the IP address, and the port numberof the switch.

While the port is in the blocked state 810, the switch can bring theport back up in response to a shut/no-shut command. For example, the sysadmin can set a shut/no-shut command to bring the port back up from theblocking state 810 to the forwarding state 804. If auto retry isenabled, the port can go back to forwarding state 804 after a timeoutperiod 812. The timeout period can be a predetermined period of timedefined in a configuration parameter. The timeout period can also bebased on a default period configured on the switch. In some embodiments,the timeout period can be set via a timeout command, which can trump ormodify the default timeout period set for the auto retry.

After the timeout period 812, the port can return to forwarding state804 and continue sending periodic MCP packets 806. The port can alsocontinue listening for MCP packets.

If during the port-up state, without checking for a loop, the port isallowed to be in forward state (MCP_FWD) and there is actually a loopand a broadcast stream is injected into the loop, this could potentiallyresult in a partial meltdown in the BD. To avoid this scenario, the portcan be operated in strict mode.

Referring to FIG. 8B, a port operation 814 in strict mode can beimplemented to bring the port up 802 after a blocked state 810 in adefault mode 816 (MCP_INIT) where only certain types of packets areforwarded and all other packets are dropped. In other words, the port indefault mode 816 can block all traffic with some exemptions for specifictypes of traffic. In some embodiments, the default mode 816 blocks alluser traffic but allows MCP packets and STP packets. In otherembodiments, the default mode 816 can include additional exemptions. Forexample, the port may allow other types of control plane packets.

During the default mode 816, the port can continue to send periodic MCPpackets 806. Moreover, if the port receives an MCP packet 808 while indefault mode 816, it can return to the blocked state 810. During theblocked state 810, the port can then return to the default mode 816after a timeout period 818 passes, if the port is configured with autoretry. Alternatively, a shut/no-shut command can be used to set the portfrom blocked state 810 to the default mode 816.

In the strict mode of operation, the port may only be allowed to move toforwarding state 804 after a grace period timeout 820. The grace periodcan be a configured value set by the switch or the system administrator.The grace period can also be modified by the administrator at any point.Moreover, the grace period can be configured based on one or morefactors, such as size of the network, amount of traffic, characteristicsof the loop, characteristics of the switch or port, time of day, type oferror, etc.

At any time, the port can also be modified to move to port operation 800in non-strict mode or port operation 814 in strict mode. Thus, the modeof the port can be modified based on the circumstances and any otherfactors.

Having disclosed some basic system components and concepts, thedisclosure now turns to the exemplary method embodiments shown in FIGS.9 and 10. For the sake of clarity, the methods are described in terms ofa system 110, as shown in FIG. 1, configured to practice the methods.The steps outlined herein are exemplary and can be implemented in anycombination thereof, including combinations that exclude, add, or modifycertain steps.

FIG. 9 illustrates a first example method embodiment. Here, the system110 receives, via a receiving port on the system 110, a miscablingprotocol packet indicating an identity of an originating switch and aport number of an originating port associated with the miscablingprotocol packet, wherein the miscabling protocol packet is received froman external network connected to the receiving port and the originatingport, and wherein the system 110 and originating switch are located onthe same network fabric (900).

The external network can be an L2 network marked as part of the samebridge domain on the system 110 and the originating switch. However, thesystem 110 and originating switch can have the external network markedas different EPGs-VLANs. On the other hand, the external network canhave the receiving port and originating port marked or configured aspart of the same VLAN. This can create a loop between the externalnetwork, the originating port, and the receiving port. For example, theoriginating and receiving ports can flood the external network withbroadcast or multicast traffic because they both see the externalnetwork as belonging to the same BD. The external network, in turn, mayforward the traffic to both the receiving and originating ports as itsees both ports as part of the same VLAN.

The originating and receiving switches can be leaf switches 304 infabric 312. Moreover, the switches can be ToR switches. Moreover, theoriginating and receiving switches can be configured to listen for MCPpackets, as well as transmit periodic MCP packets.

Next, the system 110 detects a loop between the receiving port, theoriginating port, and the external network based on the miscablingprotocol packet (902). In some cases, the miscabling protocol packet isaddressed to a multicast address, such as an MCP multicast address or anSTP multicast address. Here, because MCP packets are sent by leaf or ToRswitches in the fabric and addressed to a multicast address, the system110 can determine that a loop exists by the fact that it has received anMCP packet. This can be because MCP packets are not supposed to bereceived by the leaf or ToR switches in the fabric from the externalnetwork.

In response to detecting the loop, the system 110 then blocks thereceiving port or the originating port. The system 110 can block one ofthe ports based on a priority associated with the ports and/or theircorresponding switches. For example, the system 110 can compare theidentity of the receiving port and switch with the identity of theoriginating port and switch, and determine which port to block based ona priority determined by comparing the identities. To illustrate, thesystem 110 can extract the originating switch's IP address and portnumber from the MCP packet, and compare that with the IP address of thesystem 110 and the port number of the receiving port. The port andswitch with the higher IP address and port number can then be set toblocked state while the switch and port with the lower IP address andport number can remain in forwarding state.

When setting a port to blocking state, the system 110 can use anon-strict mode or a strict mode. In the non-strict mode the port isblocked and can be automatically returned to forwarding state after atimeout period or a shut/no-shut command. On the other hand, in thestrict mode, the port can be blocked and, after the timeout period,instead of returning to forwarding mode, it can be set to a default modethat only allows certain types of traffic, such as MCP or STP traffic,for example.

In some cases, the MCP packet can also include one or more additionalfields. For example, the MCP packet can include a timestamp and/or achecksum value. The timestamp can be used to verify that the MCP packetwas not part of an attack, such as a replay attack. Similarly, thechecksum can be used to verify that the MCP packet is authentic and notpart of a malicious attack. The system 110 can use a pre-shared key usedto generate the checksum to verify the checksum. The checksum can begenerated by a checksum function or algorithm, such as MD-5 or SHA-1, asone of ordinary skill in the art will readily understand.

FIG. 10 illustrates a second method embodiment. Here, the system 110 islocated on a network fabric and first sends, via an originating port onthe system 110, an MCP packet indicating an identity of the system 110and a port number of the originating port, wherein the originating portis a non-fabric port on the system 110, and wherein the MCP packet issent from the originating port to an external network connected to theoriginating port, and wherein the originating switch and originatingport are also located at the network fabric and connected to theexternal network (1000). Here, the network fabric can be fabric 312illustrated in FIG. 3, and the system 110 can be a leaf switch 304, asillustrated in FIG. 3. The external network can be, for example, an L2network, such as L2 network 306 illustrated in FIG. 3.

In some embodiments, the system 110 can generate and/or send periodicMCP packets as part of a miscabling protocol implemented to detect loopsinvolving the network fabric. The system 110 can also be configured toinstantiate, or listen for, MCP packets that ingress on its ports. Thesystem 110 can also send MCP packets on its ports for each EPG or VLANconfigured on its ports. This can ensure that loops are detected acrossEPGs and VLANs where they would not otherwise be detected by STP.

Next, a receiving switch located on the network fabric receives, via areceiving port, the MCP packet (1002). Based on the MCP packet, thereceiving switch detects a loop between the receiving port, theoriginating port, and the external network (1004). Here, the externalnetwork can be marked on the system 110 and the receiving switch asbeing in the same bridge domain, while the originating and receivingports can be marked on the external network as being on the same VLAN,thus creating a loop when a broadcast is transmitted to the externalnetwork via the originating or receiving ports.

Moreover, the receiving switch can be a leaf switch 304, as illustratedin FIG. 3. In some embodiments, the receiving switch is a ToR switch onthe fabric 312. The receiving switch can identify or detect the loopbased on a receipt of the MCP packet. Since the MCP packet was sent froma non-fabric port on the system 110 to the external network andaddressed to a multicast address, the MCP packet should not be returnedto any of the switches on the fabric 312 unless a loop exists betweenthe fabric 312 and the external, L2 network. To detect or identify theloop, the receiving switch can extract the identity or address of theoriginating switch (i.e., system 110) as well as the port number of theoriginating port, and compare the extracted information with theidentity or address of the receiving switch and port number of thereceiving port.

In some cases, the receiving switch and the system 110 can be the samedevice. Here, the loop would be a self-loop or hairpin loop. In othercases, the receiving switch and the system 110 can be separate leafswitches 304 on the fabric 312.

Next, the receiving switch or the system 110 can block the receivingport or the originating port in response to detecting the loop. Forexample, the receiving switch or the system 110 can select a port toblock from the originating port and the receiving port. The selectedport to block can be based on one or more factors, such as current orfuture load, subnet, statistics, priorities, preferences, etc. In someembodiments, the selected port is selected based on a comparison ofpriorities between the system 110 and the receiving switch. Moreover,when blocking a port, the switch can operate the port in strict mode ornon-strict mode, as illustrated in FIGS. 8A and 8B.

For clarity of explanation, in some instances the present technology maybe presented as including individual functional blocks includingfunctional blocks comprising devices, device components, steps orroutines in a method embodied in software, or combinations of hardwareand software.

Although a variety of examples and other information was used to explainaspects within the scope of the appended claims, no limitation of theclaims should be implied based on particular features or arrangements insuch examples, as one of ordinary skill would be able to use theseexamples to derive a wide variety of implementations. Further andalthough some subject matter may have been described in languagespecific to examples of structural features and/or method steps, it isto be understood that the subject matter defined in the appended claimsis not necessarily limited to these described features or acts. Forexample, such functionality can be distributed differently or performedin components other than those identified herein. Rather, the describedfeatures and steps are disclosed as examples of components of systemsand methods within the scope of the appended claims. Moreover, claimlanguage reciting “at least one of” a set indicates that one member ofthe set or multiple members of the set satisfy the claim.

We claim:
 1. A computer-implemented method comprising: receiving, via areceiving non-fabric port on a receiving switch located on a networkfabric, a miscabling protocol packet indicating an identity of anoriginating switch on the network fabric and an originating non-fabricport associated with the originating switch, wherein the miscablingprotocol packet is received from an external network connected to thereceiving non-fabric port, wherein the originating switch andoriginating non-fabric port are also located on the network fabric andconnected to the external network, wherein the receiving non-fabric portand the originating non-fabric port are both: on a same flood domain inthe network fabric; associated with different virtual local areanetworks or endpoint groups associated with the network fabric; andassigned to a same virtual local area network on the external network;and based on the miscabling protocol packet, detecting a loop betweenthe receiving port, the originating port, and the external network; andblocking at least one of the receiving port and the originating portassociated with the miscabling protocol packet in response to detectingthe loop.
 2. The computer-implemented method of claim 1, wherein themiscabling protocol packet further indicates at least one of a timestampand a checksum value associated with the miscabling protocol packet. 3.The computer-implemented method of claim 2, further comprising verifyingan authenticity of the miscabling protocol packet based on at least oneof the timestamp and the checksum value.
 4. The computer-implementedmethod of claim 1, wherein the miscabling protocol packet is addressedto a multicast address associated with a miscabling protocol, andwherein at least one of the originating non-fabric port and thereceiving non-fabric port is connected to an overlay network.
 5. Thecomputer-implemented method of claim 1, wherein the receiving switchcomprises a leaf switch, and wherein the network fabric is based on aspine-leaf topology.
 6. The computer-implemented method of claim 1,wherein detecting the loop is based on a receipt of the miscablingprotocol packet by the receiving switch.
 7. The computer-implementedmethod of claim 1, wherein identifying the loop is further based on adifference between a first address associated with the originatingnon-fabric port and a second address associated with the receivingnon-fabric port.
 8. The computer-implemented method of claim 1, whereindetecting the loop is further based on at least one of a firstdetermination that the originating switch is also the receiving switchand a second determination that the originating non-fabric port is alsothe receiving non-fabric port.
 9. The computer-implemented method ofclaim 1, wherein the external network comprises a layer 2 network. 10.The computer-implemented method of claim 9, wherein the layer 2 networkis set at the receiving non-fabric port and originating non-fabric portas a same bridge domain.
 11. The computer-implemented method of claim 1,wherein the receiving switch is configured to send at least onemiscabling protocol packet periodically at configured intervals.
 12. Thecomputer-implemented method of claim 1, wherein the receiving switch isconfigured to listen to miscabling protocol packets.
 13. Thecomputer-implemented method of claim 1, further comprising: sending atleast one miscabling protocol packet for each configured virtual localarea network on each of a plurality of non-fabric ports on the receivingswitch, and wherein detecting the loop is based on a determination thatthe miscabling protocol packet was sent by the originating non-fabricport over a first virtual local area network or endpoint group andreceived by the receiving non-fabric port on a second virtual local areanetwork or endpoint group that is different than the first virtual localarea network or endpoint group.
 14. The computer-implemented method ofclaim 1, wherein blocking at least one of the receiving non-fabric portand the originating non-fabric port is based on respective identities ofthe receiving non-fabric port and the originating non-fabric port, themethod further comprising unblocking the at least one of the receivingnon-fabric port and the originating non-fabric port after a timeoutperiod.
 15. The computer-implemented method of claim 14, wherein theunblocking is based on a strict mode where only one or more specifictype of packets are allowed and other packets are blocked for at least aperiod of time.
 16. A system comprising: a processor; and acomputer-readable storage medium having stored therein instructionswhich, when executed by the processor, cause the processor to performoperations comprising: receiving, via a receiving non-fabric port in anetwork fabric, a miscabling protocol packet indicating an identity ofan originating switch in the network fabric and an originatingnon-fabric port associated with the miscabling protocol packet, whereinthe miscabling protocol packet is received from an external networkcoupled with the receiving non-fabric port, and wherein the originatingswitch, the originating non-fabric port and the receiving non-fabricport are all located on the network fabric and coupled with the externalnetwork, and wherein the receiving non-fabric port and the originatingnon-fabric port are both: on a same flood domain in the network fabric;assigned to different virtual local area networks or endpoint groups inthe network fabric; and assigned to a same virtual local area network onthe external network; and based on the miscabling protocol packet,identifying a loop between the receiving non-fabric port on the networkfabric, the originating non-fabric port on the network fabric, and theexternal network; and re-configuring at least one of the originatingnon-fabric port and the receiving non-fabric port.
 17. The system ofclaim 16, wherein re-configuring at least one of the originatingnon-fabric port and the receiving non-fabric port comprises blocking atleast a portion of traffic on at least one of the originating non-fabricport and the receiving non-fabric port.
 18. The system of claim 16,wherein identifying the loop is based on at least one of: adetermination that: the system comprises both the originating switch anda receiving switch associated with the receiving non-fabric port; andthe system has both originated the miscabling protocol packet andreceived the miscabling protocol packet from the external network; or adetermination that: the miscabling protocol packet was originated by anon-fabric port located in the network fabric where the receivingnon-fabric port resides; and the miscabling protocol packet was sent bythe originating non-fabric port towards the external network via a firstvirtual local area network or endpoint group and received by thereceiving non-fabric port from the external network via a second virtuallocal area network or endpoint group that is different than the firstvirtual local area network or endpoint group.
 19. The system of claim16, wherein re-configuring at least one of the originating non-fabricport and the receiving non-fabric port comprises blocking a selected oneof the originating non-fabric port or the receiving non-fabric port, theselected one of the originating non-fabric port or the receivingnon-fabric port being selected based on a comparison of a first addressassociated with the originating switch and a second address associatedwith the system.
 20. A computer-readable storage hardware device havingstored therein instructions which, when executed by one or moreprocessors, cause the one or more processors to perform operationscomprising: receiving, from an external network and via receivingnon-fabric port on a receiving switch located on a network fabric, amiscabling protocol packet indicating an identity of an originatingswitch on the network fabric and an originating non-fabric portassociated with the originating switch, the receiving non-fabric portand the originating non-fabric port being connected to the externalnetwork, wherein the originating non-fabric port and the receivingnon-fabric port are both: on a same flood domain in the network fabric;mapped to different virtual local area networks or endpoint groups onthe network fabric; and assigned to a same virtual local area network onthe external network; and based on the miscabling protocol packet,detecting a loop between the receiving non-fabric port, the originatingnon-fabric port, and the external network; and blocking at least one ofthe receiving non-fabric port and the originating non-fabric port. 21.The computer-readable storage hardware device of claim 20, whereindetecting the loop is based on a determination that the receiving switchand the originating switch are both located in the network fabric. 22.The computer-readable storage hardware device of claim 20, wherein thereceiving switch and the originating switch are a same switch.
 23. Thecomputer-readable storage hardware device of claim 20, wherein thereceiving switch and the originating switch comprise leaf switches onthe network fabric, and wherein the leaf switches are top-of-rackswitches.
 24. The computer-readable storage hardware device of claim 20,storing additional instructions which, when executed by the processor,result in operations further comprising: generating miscabling protocolpackets; and sending, via the receiving switch, the miscabling protocolpackets to each endpoint group or virtual LAN configured on thereceiving switch, wherein the miscabling protocol packets have at leastone of a multicast or broadcast destination address, wherein each of themiscabling protocol packets includes a first indication that thereceiving switch originated the miscabling protocol packet and a secondindication identifying which non-fabric port on the receiving switchtransmitted the miscabling protocol packet.
 25. The computer-readablestorage hardware device of claim 24, storing additional instructionswhich, when executed by the processor, result in operations furthercomprising: periodically sending the miscabling protocol packets to themulticast or broadcast destination address.